Heater



April 1933- F. T. POWERS 78.

HEATER I Filed Oct. 20, 1931 2 Sheets-Sheet l 70 ource April 18, 1933. F. T. POWERS 1,903,878

HEATER Filed Oct. 20, 1931 1 2 Sheets-Sheet 2 INVENTOR Patented Apr. 18, 1933 I UNITED STATES PATENT OFFICE FRANK n rownns, or nonGLAs'roN, NEW YORK HEATER Application filed October 20, 1931. Serial No. 570,026.

My invention relates to the art of making printing plates by photo mechanical processes and particularly to a process and apparatus for heating plates to set the resist which is 5 applied to the platesin powder form during theprocessof etching.

The objects of my invention are to provide a process and apparatus whereby the metal plates may be automatically heated quickly and uniformly to the desired temperature,

and which will be susceptible to such variation in heating power as may be necessary to properly heat plates of varying thicknessand size.

" to protect the shoulders of the lines or dots forming the design, soth'at the etching proc ess may be carried to a depth which will give satisfactory printing quality to the plate. The etching process is carried out in a series of stages or steps called bites and before the etching of each bite the etcher applies a resist which is usually dragons blood in powdered form by brushing it up against the sides or shouldersof the linesor dots with a soft brush, brushing in one direction only across the plate. After the brushing operation the plate is heated uniformly to a temperature which will fuse or melt the dragons blood and cause it to adhere to the plate. The

V plate is then cooled, usually with the aid of water applied to the back of the plate, and another application of powder is made. The brushing is done in a direction either at right angles or opposite to the previous brushing.

" Again the plate is heated to the melting point of the powder, cooled, and these operations are repeated until the 'plate has been pow dered four ways, in the parlance of the trade. Of the op'eartions involved in powdering a plate, those of brushing the powder and heating the plate require skill and experience, in that both operationsmust be done uniformly over the entire surface and carried to just the proper degree. I am aware that numerous devices have been designed and in vented for performing the heating operation by processes and apparatus intended to reduce the time required and to give a uniform heat over the entire plate,but by means of my new process and apparatus I have cut the heating 5 time to aboutone half the time required with other types of heating devices and produced exceedingly uniform results.

In" the drawings, Fig. l is a side view and Fig. 2 is a plan view, of one of the preferred embodiments of my invention. Figs. 3 and 4: are details which will be described. In these drawings like symbols refer to the same or similar parts and arrows indicate direction of rotation, movement or flow.

- In Figs. 1 and 2, the main framework 1 forms the support, for two chain conveyors, one of which consists of sprockets 2 and 3, cooperating with detachable link chains 4:

.and 5 which carrya plurality of cross bars 6, each of which is provided with a plurality of vertical projecting fins 7' which prevent the plate being heated'from'slipping over or under the cross bars. A second chain conveyor consists of sprockets 8 and 9 coopcrating with chains 10 and 11. This conveyor also carries aplurality of cross bars 12 which are also provided with vertical fins 13 to keep the plate from slipping over or'under the cross bars. The cross bars 6 ride upon a plurality of grid bars 14, ar-

ranged side by side, but spaced apart and extending lengthwise of the machine from the sprockets 2 to sprockets 3, where they terminate to permit the cross bars 6 to be carried around the sprockets 3 by the chain 4. A second set of grid bars 15, also extend lengthwise of'the machine from between sprockets 8, to between sprockets 9, and upon these grid bars ride the cross bars 12. The two conveyors are driven by a motor 16 through a belt 17, cooperating'with a pulley 18, mounted on the shaft 19, which also car- .ries sprockets 2. The second conveyor is driven by the first conveyor by means of the spur gears 19 and 20, which are mounted respectively on the shafts which also carry sprockets .3 and 8 Beneath the grid bars 15 are located a plurality of gas burner pipes 21, each of which is provided with a plurality of gas burner tips 22, so arranged that there is a burner tip in each burner pipe within each space between grid bars 15. The burner tips 22 are of the well known screen type for burning high pressure gas and are especially designed to prevent back fire. The burner pipes 21 are each provided with air inlet controls 24, by means of which the mixture of gas and air is adjusted to give the desired conditions of combustion. All burner pipes are connected to a header or manifold 25, which is supplied with high pressure gas through pipe 26, in which is the valve 27 operated by the solenoid 27a. A gas compressor 28 driven by a motor 29 receives low pressure gas from any convenient source of supply, such as the city main, through the pipe 30, and discharges it at a pressure of from 4 to 6 lbs. into the pipe 31, which is connected to the gas tank 32, and also to the solenoid operated valve 27. The gas tank 32 is provided with a pressure gauge 33. A pilot light 34 connected to a source of supply of gas is provided to ignite the gas issuing from burner tips 22, when the heater is started up. Above the burners is supported by suspension from above, a bafiie 35 of heat resistant material, such for example, as fire brick or carborundum. Above the baffle 35, and covering the area of the heating elements, is provided a hood 36, of sheet metal or other suitable material, which is preferably connected by duct 32 to a ventilating pipe, not shown, to carry ofi the heated gases.

The automatic operation of my new heater is provided for as follows: A rocking bar 38 passes through holes in the grid bars 15, and is provided with an upwardly projecting lug 39, which extends above the tops of the grid bars 15. On one end of the rocking bar 38 is mounted a mercury bulb switch 40, of well known type, consisting of a small glass bulb containing mercury, and into which are sealed the terminals of two wires, the whole arranged in such a manner that when the bulb is tilted in one position, the circuit between the two terminals is closed by the mercury and when the bulb is tilted in another position the circuit is broken.

The two wires 41, of the mercury switch, lead to a solenoid operated time switch 42, of well known design, set to open the circuit closed by the mercury switch 40, after such time as may be desired. The solenoid operated time switch 42, controls the closing and opening of two electric circuits, one 43, leading to the solenoid 27a of the gas valve 27, and the other 44, leading to the motor 29.

Having described my new heating apparatus, I shall now describe its operation.

The motor 16 having been started and the pilot light 34, having been lighted and the compressor 28, having been operated for a few seconds to build up a pressure of gas in the storage tank, a plate to be heated is placed on the grid bars 14, between two of the cross bars, in such a position as indicated at (a) in Figs. 1 and 2. The plate is pushed forward in the direction indicated by the arrows by the cross bar 6, while riding on the tops of grid bars 14. The plate is passed from grid bars 14 to grid bars 15, where it is left by cross bar 6, which is carried over the end of grid bars 14, as it passes around sprockets 3. The plate is then pushed forward by one of the cross bars 12, over the gas burner pipes 21. The plate is now in position (6) and just entering the heating zone. At this point the front edge of the plate engages the lug 39, on the rocker bar 38, tipping it over suiiiciently to tilt the mercury switch 40, and close the circuit 41. The time switch 42 is thereby operated to close circuits 41 and 43 simultaneously opening the gas valve 27, and starting the motor driven compressor 28. The gas-air mixture issuing under high pressure from all of the gas tips 22 is immediately ignited by the pilot light 34, subjecting the plate to an intense heat during the period of time in which the plate is pushed by the cross bar 12, over all the burners. Having passed through the heating zone the plate is deposited on the table 45, in position C, as the cross bar 12 is carried upward around sprockets 9.

The time switch 42 is so adjusted as to open the circuits 41 and 43 after a period of time, usually 5 to 7 seconds, has elapsed after the plate has passed over the lug, 39, and has permitted the mercury switch 40, to swing back to its normal position and so open the circuit 41.

If a second plate should be following after the first plate and should reach and tilt the rocker bar 34, before the time switch 42 has opened the circuits closed by the passage of the first plate, then in that event the time switch 42 is reset by the passage of the second plate and does not open circuits 41 and 43 until the lapse of 5 to 7 seconds after the passage of the second plate. Similarly a third or fourth plate will delay the opening of circuits 41 and 43, and consequently delay the shutting off of the gas and stopping the compressor until 5 to 7 seconds has elapsed after its passage over the lug 39. In order that the rocker bar 38 may not be tilted by the passage of the cross bars 12, these cross bars are constructed with a hump, as shown in Figs. 3 and 4. By this arrangement the cross bars do not contact with the lug 39, but a fiat plate does so contact and so operates the mercury switch 40.

In some cases, namely, those in which a supply of gas is available at high pressure, such as 2 lbs. or more, the compressor 28, its motor 29, control circuit 44 and the gas tank 32 become unnecessary and may be omitted since gas is under those circumstances always available and requires no boosting from low to high pressure. 7

In the making of printing plates by the process herein described, it has recently become common to use a heavier plate of metal for certain purposes. This heavier metal is slower to heat with the heating devices. in common use, but because of the intensity of the flame and the accurate adjustment of the mixture of air and gas passing through the burner, these thick plates are perfectly heated in the same time interval as the standard weight thinner plates.

The artificial gas, usually available in those cities and towns which are not served with natural gas, is so-called water gas and has a heating value of only about 500 B. t. u. per cubic foot, whereas natural gases ordinarily have a heating value of about, 950 or 1000 B. t. u. per cu. ft. It is generally diflicult or impossible using artificial gas at the pressures under which it is ordinarily supplied to the consumer, namely, equivalent to a head of from 2 to 5 inches of water, to burn enough gas under these conditions to heat a plate of standard thickness, in less than 12 seconds, or to heat the heavier plate to the desired temperature in less than fifteen to eighteen seconds. To shorten this time required for burning in various expedients have beenresorted to, such as the preheating of. an oven o-rlmufiie into which the plate is placed and heated in a shorter time than is required when only the direct heat from the gas burner is used. The time required to heat up such an oven or mulfie isconsiderabla many minutes, and in warm weather especially the resulting heat in the room is objectionable. 7 These objections and others inherent in the previous known form of heaters, are overcome by my invention.

The present invention is especially well adapted to use as the heating element or section of the continuous automatic powdering machine for patent on which applicant has co-pending application Ser. No. 513,364.

By means of my'present invention, I'eliminate the necessity'for heating up the stove section of acontinuous automatic powdering machine previous to beginning the operation of powdering a plate. Ordinarily there is a delay of some 15 to 30-minutes, during which time the heating section of the machine is heated to such a temperature that a plate will be properly and uniformly burned in while passing through the stove at the normal operating speed of the machine, or when separately burned in by hand.

I have described herein a preferred form of apparatus, embodying the spirit of my inused without departing from the spirit thereof, and I do not confine myself to this particular device or arrangement but only to those combinations of parts set forth in the appended claims which describe the invention.

I claim:

1. An apparatus for heating photo-mechanical printingplates comprising in cooperative combination conveying means for the plates, a source of supply of gaseous fuel,

a compressor, means controlled electrically.

for driving said compressor, a plurality of high pressure gas burners operatively connected by duct to the discharge aperture of said compressor, a storage tank between said compressor and said burners, an electrically operated gas valve in said duct, and electrical controlling means operable by the passage of the plate for starting the said compressor and opening said gas valve.

2. An apparatus for heating photo-mechanical printing plates, consisting of the cooperative combination of a support for the plate to be heated, means for passing the plate along saidsupport at a pre-determined speed, a plurality of high pressure gas burners beneath said support, a gas compressor. a gas receiving tank, an electrically operated gas valve in a duct connecting the gas compressor and tank to said gas burners, an electrical time switch arranged to be placed in'operation by the passage of the plate, and arranged to cause the compressor to run and the gas valve to open and remain open a predetermined period of time. I

3. An apparatus for the purpose described which is characterized by having in cooperative arrangement a conveying means for the plates to be heated, high pressure gas burntank, means actuated by the first of a plurality of plates passing along said conveyor for simultaneously admitting gas to said burners and starting said compressor, and means for shutting off said gas and stopping said compressor at a pre-determined time after the passage of the last of the said .plurality of plates.

Signed at New York city, New York and State of New York this 15th day of Sept. A. D. 1931.

FRANK T. POWERS.

vention, but it will be obvious to one skilled V in the art that numerous modifications may be made and other arrangements of parts in the county of 

